When switching devices interrupt high currents, in particular short-circuit currents, electric arcs form in the interrupting chambers thereof. In “Niederspannungs-Leistungsschalter [Low-Voltage Circuit-Breakers]”; Berlin, Heidelberg, New York 1979, pages 59 through 62, Franken describes the following methods for quenching electric arcs: extending the length of the arc, cooling the arc, and dividing the arc. In the arc-cooling method, the intensive cooling of the arc is essentially accomplished by contact with insulating parts or cooling plates. In the arc-division method, the electric arc is driven by magnetic forces into a system of arc splitter plates disposed in a parallel or curved arrangement, the arc being divided into several partial arcs, which results in a considerable increase in the voltage losses within the entire arc. In comparison with arc splitter plates, cooling plates are simpler and, therefore, less expensive to manufacture, but inferior in terms of the magnitude of the arc current to be extinguished.
DE 41 09 717 C1 discloses a contactor including an electromagnetic operating mechanism which is arranged in a multi-part housing, switching contacts which are accommodated in an interrupting chamber, and further including arc splitter plates which are associated with the switching contacts and form extinguishing chambers, and which are accommodated in a top housing part which can be closed by a cover. The arc splitter plates, which are assembled by means of insulating plates to form arc splitter plate stacks and are inserted into the housing chambers, are resiliently pressed and clamped against the wall of the top housing part by means of end legs of commutation plates, said end legs being bent in a double U-shape.
In a contactor according to DE 198 14 411 C1, the uppermost arc splitter plate, which faces the cover and is designed as a shield plate, has two clips which are bent upward. Recesses corresponding to the clips are formed on the inner side of the cover. The extinguishing chambers can be fastened to the cover by inserting the clips in the recesses, forming a positive-locking joint.